1. Field of the Invention
The present invention relates to a method for sharing and updating a key, and more particularly, to a method for sharing and updating a key safely and efficiently, using a watermark inserted into an image to prevent illegal copy, forgery and falsification of the image.
2. Description of the Related Art
Network communication is vulnerable to intruders' attacks. Therefore, encryption is used for secure communication and thus a key sharing and update mechanism is required for the encryption.
In general, to provide a key sharing and update function between a terminal and a server or between terminals, a key management module should be separately operated. In addition, when a key is shared and updated, a secure channel should be established mutually and a key value should be transmitted via the secure channel. In other words, many elements are additionally needed to implement a key sharing and update mechanism.
A watermark may be inserted into an image to prevent illegal copy, forgery and falsification of the image. Intellectual property right information, content information, a user Identifier (ID), etc. are available as watermarks.
FIG. 1 illustrates a conventional operation for inserting a watermark into an image and extracting the watermark from the image.
Referring to FIG. 1, upon receipt of an image through a camera 110, a transmitter 120 inserts a watermark value 130, W into an image during encoding the image. The watermark value 130, W is inserted into a predetermined parameter during the encoding, or into a predetermined parameter extracted from the image after the encoding. The latter method is usually used when an image is encoded or a watermark is inserted into an image, without modifying a Coder and Decoder (CODEC).
The coded image is transmitted as a bit stream to a receiver 140. The receiver 140 extracts a watermark value 150, W′ from the image during decoding the image and compares the watermark value W with the watermark value W′. If the watermark values W and W′ are equal, the receiver 140 outputs an image 160 and otherwise, the receiver 140 notifies a manager or a user that the image was forged or falsified.